Multilayer core-shell microsphere as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of fireworks and crackers, and relates to a multi-layer core-shell microsphere, a preparation method thereof and application of the multi-layer core-shell microsphere in fireworks. The multi-layer core-shell microsphere comprises a four-layer structure including an inner core layer, a reduction catalyst layer, an adsorption layer and a coating layer, the inner core layer is coated with a reduction catalyst layer, the reduction catalyst layer is coated with an adsorption layer, and the adsorption layer is coated with a coating layer; the inner core layer is composed of a carrier material, the specific surface area of the carrier material is 200-500 m < 2 > / g, and the porosity is 0.4-0.8 cm < 3 > / g; and the reduction catalyst layer comprises a reducing agent and a catalyst. Through the synergistic effect of the four-layer structure, the reaction efficiency is improved in the combustion stage, generation of pollutants is reduced from the source, gaseous pollutants and heavy metal particles are adsorbed and fixed instantly after setting off, and meanwhile agglomeration and sedimentation of the particles are promoted by means of a carrier. Compared with traditional fireworks, the PM2.5 concentration is reduced by 35-50%, and the problem of total pollution control is effectively solved.

Description

Technical Field

[0001] This invention belongs to the field of fireworks and firecrackers technology, specifically relating to a multilayer core-shell microsphere, its preparation method, and its application in fireworks. Background Technology

[0002] Traditional fireworks typically use black powder as a propellant, whose main components are a mixture of potassium nitrate, charcoal, and sulfur. However, this traditional formula has significant drawbacks: it is highly sensitive during production and transportation, making it prone to safety accidents; and when ignited, the sulfur-containing components produce harmful gases such as sulfur dioxide, severely polluting the atmosphere and endangering human health.

[0003] In recent years, to address environmental pressures, the industry has developed some alternatives to black powder. For example, some new types of fireworks propellants use potassium perchlorate as an oxidizer, combined with combustibles such as terephthalic acid, potassium hydrogen terephthalate, and charcoal powder, as well as phenolic resin as a binder. While these formulations reduce sulfur pollution to some extent, they still fail to solve the problem of fine particulate matter pollution generated during the fireworks display, and their effectiveness in controlling heavy metal pollutants is limited.

[0004] In the field of catalyst coating technology, various coating methods have been developed for different purposes. For example, the boron nitride-coated cerium-based platinum group single-atom catalyst developed by Jiangnan University enhances the thermal stability of the catalyst by regulating the coordination structure of the metal center through the boron nitride inert layer. The carbon-encapsulated copper-zinc-aluminum catalyst researched by Guangdong University of Technology effectively inhibits the migration and aggregation of the active component, elemental copper, by using carbon coating. The cobalt-coated carbon-supported platinum catalyst developed by Tsinghua University forms a core-shell structure through the cobalt coating layer, enhancing the interaction between the catalyst supports. However, the above coating technologies are mainly applied in the field of industrial catalysis, and there are no reports of their application in fireworks formulations to simultaneously address pollution control and combustion efficiency issues. Especially in terms of particulate matter settling and heavy metal fixation after fireworks displays, existing technologies lack targeted solutions.

[0005] The latest research on environmentally friendly fireworks attempts to reduce pollution from the formulation perspective. For example, existing technology CN119874462A, patented as a high-explosive-heat-desensitive environmentally friendly fireworks propellant, uses ultrafine metal powder as a combustible agent, high-molecular fluoride as an oxidizer, and introduces a high-energy desensitive energetic material 3-nitro-1,2,4-triazol-5-one (NTO) to increase the explosive heat and projectile height. Although this type of formulation reduces sensitivity, it is still insufficient in treating solid particulate matter after combustion and cannot effectively control the emission of inhalable particulate matter such as PM2.5 and PM10.

[0006] Another research direction is CN119841698A, a patent titled "A Firework Propellant Containing a Fluorine Binder." This involves dissolving Fe3O4, CuO, and polyvinylpyrrolidone into a mixed solution; dissolving RDX in acetone and adding it to the mixed solution to allow the RDX to recrystallize and precipitate, obtaining a modified RDX explosive; mixing aluminum powder, magnesium powder, and boron powder under an inert atmosphere to obtain an active metal powder; adding polytetrafluoroethylene powder, modified RDX explosive, and active metal powder to obtain a premixed composite powder; and mixing the binder fluororubber and polyvinylidene fluoride in ethyl acetate, adding the premixed composite powder, and granulating to obtain a fireworks propellant containing a fluorine binder. This achieves controllable burning rate and the product is sulfur-free, nitrogen-free, and produces minimal smoke. However, this type of formulation primarily addresses the environmental friendliness of the propellant itself, while not comprehensively considering the widespread pollutants generated after fireworks explosions.

[0007] Furthermore, existing technologies neglect the reliance on total emission control. Literature research clearly indicates that environmentally friendly fireworks are not truly "green." Their improvement is offset by large-scale deployment. Simulations show that using twice the quantity of environmentally friendly fireworks produces pollution comparable to traditional fireworks. This reveals a fundamental limitation of existing technological approaches: focusing solely on formula improvements while ignoring the crucial variable of "total emission," thus failing to achieve true source control. Summary of the Invention

[0008] The purpose of this invention is to provide a multilayer core-shell microsphere, its preparation method, and its application in fireworks, so as to simultaneously solve the problems of low combustion efficiency, high instantaneous concentration of pollutants, and long suspension time of particulate matter during fireworks display.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A multilayer core-shell microsphere comprises a four-layer structure consisting of a core layer, a reduction catalytic layer, an adsorption layer, and a coating layer; the core layer is coated with a reduction catalytic layer, the reduction catalytic layer is coated with an adsorption layer, and the adsorption layer is coated with a coating layer.

[0011] The core layer is composed of a carrier material with a specific surface area of ​​200-500 m². 2 / g, porosity 0.4-0.8 cm 3 / g;

[0012] The reduction catalytic layer includes a reducing agent and a catalyst;

[0013] The adsorption layer includes an adsorption material;

[0014] The coating layer is a biodegradable polymer protective film.

[0015] The four layers of the multilayer core-shell microspheres of this invention—the core layer, the reduction catalytic layer, the adsorption layer, and the coating layer—exhibit a significant synergistic effect, the principle of which is explained below:

[0016] Core-reduction catalytic layer: The core consists of a high specific surface area (≥200 m²) 2 The core, composed of a support with high porosity (g) and high density, provides a suitable loading platform for the reducing agent and catalyst, ensuring their high dispersion and thus maximizing catalytic efficiency.

[0017] Mechanisms ensuring highly dispersed reduction catalyst layer: ① Support pretreatment: Calcination at 300-500℃ activates the support surface, increasing active sites such as hydroxyl groups and enhancing catalyst anchoring ability. ② Ultrasonic-assisted loading: Ultrasonication at 40kHz and 300W for 40 minutes forces some catalyst precursors and some reducing agents to uniformly penetrate into the support pores. ③ Calcination and solidification: Calcination at 300-500℃ under an inert atmosphere decomposes the catalyst precursors into oxides and firmly adheres to the support. ④ Effect verification: The catalyst prepared in Example 1 is uniformly distributed on the biochar surface, and the combustion efficiency is improved by 15%.

[0018] Reduction Catalytic Layer-Adsorption Layer: The reduction catalytic layer improves combustion efficiency at the source, reducing the generation of incomplete combustion products (such as CO and soot), thereby directly reducing the pollutant load that the subsequent adsorption layer needs to treat. At the same time, the high temperature generated by combustion provides conditions for the activation of the adsorption layer.

[0019] The effects of the adsorption layer on the reduction catalyst layer: ① Positive effect: The adsorption layer is located outside the catalyst layer. After the coating layer degrades during fireworks display, the adsorption layer can capture intermediate pollutants (such as CO) generated by the incomplete oxidation of the catalyst layer, preventing the catalyst layer from being contaminated and reducing catalytic efficiency. ② Temperature protection: The adsorption layer (such as modified activated carbon) has a heat resistance of ≥600℃, preventing the catalyst layer from being directly exposed to high-temperature flue gas, which could lead to sintering deactivation. ③ Data support: Example 3 (complete structure) reduced PM2.5 emissions by 52%, far exceeding Comparative Example 7 (layer sequence reversed, only 28%).

[0020] Adsorption Layer - Coating Layer: The coating layer protects the adsorbent material from moisture or physical damage during storage and transportation, ensuring its adsorption activity. During fireworks display, the coating layer rapidly degrades, precisely releasing the adsorbent layer to capture gaseous pollutants and heavy metals generated instantaneously.

[0021] The influence of the adsorption layer on the coating layer: ① Triggering of coating layer degradation: The high specific surface area (≥800m² / g) of the adsorption layer rapidly absorbs heat during combustion, accelerating the melting and degradation of the coating layer (such as PVA) and releasing the internal functional layer. ② Physical support: The adsorption layer provides a flat substrate for the coating layer, ensuring uniform coating thickness.

[0022] Synergistic sedimentation effect: The core carrier fixes and aggregates the captured fine particulate matter (such as PM2.5) into larger and heavier aggregates, which significantly accelerates the sedimentation rate of particulate matter. The catalytic layer improves energy utilization efficiency while reducing emissions.

[0023] The specific four-layer structure of this invention achieves pollution control and combustion efficiency enhancement through the synergistic effect of source reduction, end-of-pipe adsorption, and carrier sedimentation:

[0024] Core layer (high specific surface area carrier): provides physical support and adsorption sites, promoting the aggregation and sedimentation of particulate matter.

[0025] Reduction catalyst layer: Improves combustion efficiency, reduces the generation of incomplete combustion products (such as CO and soot), and reduces end-of-pipe treatment load.

[0026] Adsorption layer: captures gaseous pollutants (SO2, NO) x (and heavy metals, fixed on the surface of the carrier.)

[0027] Coating layer: Protective functional layer during storage, which rapidly degrades and releases active components during combustion.

[0028] This invention utilizes a four-layer core-shell structure microsphere comprising an inner core layer, a reduction catalytic layer, an adsorption layer, and a coating layer to achieve organic synergy and temporal coupling of functional components. In the initial stage of fireworks display, the coating layer (e.g., a polyvinyl alcohol protective film) rapidly degrades at high temperatures, releasing internal active components. Subsequently, the heat and flame generated by combustion first act on the adsorption layer. This adsorption layer is composed of porous materials with a heat resistance temperature ≥600℃ and a high specific surface area (e.g., modified activated carbon, molecular sieves). At high temperatures, it not only maintains structural integrity but also acts as a heat buffer and conductive medium. Heat is efficiently conducted through the solid framework of the adsorption layer, activating it and preparing it for subsequent adsorption. Simultaneously, the gaseous oxidizing substances (e.g., oxygen, chlorine oxides) and some reactive gases produced by the thermal decomposition of oxidizing agents (e.g., potassium perchlorate) diffuse through the pore network of the adsorption layer, reaching the internal reduction catalytic layer. Here, reducing agents (such as aluminum powder) and catalysts (such as CuO / Fe2O3) are pre-loaded uniformly onto a high specific surface area core support, forming a highly efficient micro-reaction interface. The diffused gaseous oxidant and reducing agent undergo a vigorous and complete redox reaction on the catalyst surface. This process not only releases a large amount of heat to maintain combustion but also significantly reduces the generation of incomplete combustion products (such as CO and soot), achieving source emission reduction. This vigorous and complete redox reaction is an explosion reaction. Subsequently, at the moment of the explosion, the adsorbed layer is dispersed into the smoke and dust, becoming adsorbed particles, which, due to their activated high specific surface area (200–500 m²),... 2 / g) Instantaneously captures gaseous pollutants (such as SO2, NO) generated after the explosion. xHeavy metal particles and other particulate matter contribute to the deposition of large amounts of pollutants; simultaneously, the core layer carriers (such as biochar or γ-Al₂O₃, with a specific surface area ≥200 m²) also contribute to the deposition of pollutants. 2 / g) serves as a fixed platform, promoting the aggregation of some pollutants into larger particles, accelerating their sedimentation, and achieving end-of-pipe treatment.

[0029] According to embodiments of the present invention, the present invention can be further optimized, and the optimized technical solution is as follows:

[0030] In one preferred embodiment, the carrier material is one or more of activated alumina, biochar, silica gel, porous ceramic microspheres, mesoporous silica, or molecular sieve.

[0031] The function of the core layer is to provide mechanical support and a large load surface area, and to provide a place for subsequent adsorption.

[0032] In one preferred embodiment, the carrier material has a compressive strength ≥5 MPa and a heat resistance temperature ≥600℃ to ensure that the structure is not damaged during the drug compression and combustion process.

[0033] In one preferred embodiment, the mass ratio of reducing agent to catalyst in the reduction catalyst layer is (3-5):1.

[0034] If the mass ratio of reducing agent to catalyst is too small (e.g., <3:1): the reducing agent is relatively insufficient, and the catalytic active sites of the catalyst cannot be fully utilized, resulting in incomplete combustion reaction and a decrease in energy release rate and emission reduction effect.

[0035] An excessively high mass ratio of reducing agent to catalyst (e.g., >5:1): Excessive reducing agent may cause the reaction to be too violent and difficult to control, and may produce more incomplete combustion products (e.g., soot) due to local oxygen deficiency, while also increasing costs.

[0036] In one preferred embodiment, the reducing agent is one or more of aluminum powder, magnesium powder, boron powder, silicon powder, titanium powder, zirconium powder, or aluminum-magnesium alloy powder, with a particle size of 1-10 μm.

[0037] If the reducing agent has a particle size that is too small (e.g., <1 μm), it will result in:

[0038] Safety hazards: Metal powders with excessively small particle size have a dramatically increased specific surface area and extremely high activity. They are highly susceptible to oxidation in air and may spontaneously combust or explode, posing significant safety risks to production, transportation, and storage.

[0039] Too fast a reaction: An excessively high specific surface area can cause the combustion reaction to be too fast, even difficult to control, which may cause the fireworks to explode instead of the expected gradual combustion, affecting the visual effect and increasing the danger.

[0040] Processing difficulties: Ultrafine powders are prone to generating dust, making them difficult to disperse evenly. Furthermore, they are prone to agglomeration during the coating process due to static electricity and other factors, affecting the uniformity of each layer structure.

[0041] High cost: The preparation of metal powders with small particle size and uniform distribution requires advanced technology, which significantly increases the cost.

[0042] If the reducing agent has an excessively large particle size (e.g., >10μm), it will result in:

[0043] Incomplete reaction: Excessive particle size leads to a decrease in specific surface area, resulting in insufficient contact area between the reducing agent, oxidant, and catalyst. This slows down the combustion reaction rate and makes it easier to form more unburned carbon particles and incomplete combustion products such as CO due to incomplete reaction, which in turn increases the emission of pollutants (such as PM2.5).

[0044] Low energy release efficiency: Incomplete reaction directly leads to a decrease in energy release rate, affecting the fireworks' ascent height, brightness, and color saturation.

[0045] Reduced synergistic effect: Oversized reducing agent particles are not conducive to the formation of uniform catalytic-reduction microregions on the support surface, which weakens the synergistic effect with the catalyst and reduces the efficiency of the core "microreactor".

[0046] Rapid settling speed: During the mixing process of the medicine, excessively heavy particles may lead to uneven distribution of components.

[0047] In one preferred embodiment, the catalyst is a transition metal oxide.

[0048] In one preferred embodiment, the catalyst is CuO, Fe2O3, Co3O4, or MnO. 2、 One or more of Cr2O3, NiO, V2O5, Pt, Pd or their oxides.

[0049] The function of the reduction catalyst layer is to reduce the activation energy of the combustion reaction, improve combustion efficiency and completeness, and reduce the generation of black smoke and incomplete combustion products from the source.

[0050] In one preferred embodiment, the adsorbent material is a porous material with a surface area of ​​200-500 m². 2 / g, porosity 0.4-0.8cm 3 / g, compressive strength ≥5MPa, ensuring no breakage during compression molding; heat resistance temperature ≥600℃, ensuring resistance to high temperatures during combustion.

[0051] In one preferred embodiment, the adsorbent is one or more of the following: modified biochar, activated carbon, metal-organic framework (MOF) materials, zeolite, diatomaceous earth, hydrotalcite, and graphene oxide.

[0052] The adsorbent material is one or more of modified biochar, activated carbon, or metal-organic frameworks (MOFs). The adsorbent material should have a high specific surface area (≥800 m²). 2 / g) and abundant porous structure, which are effective against SO2 and NO. x It exhibits high selective adsorption capacity for gases and heavy metal particles, and possesses good thermal stability, maintaining structural stability in the high-temperature flue gas after combustion. In one preferred embodiment, the modified biochar is phosphorylated biochar or KOH-activated biochar.

[0053] The function of the adsorption layer is to efficiently adsorb and fix gaseous pollutants (SO2, NO) in the flue gas within a very short time after the explosion. x (and heavy metal particles.)

[0054] In one preferred embodiment, the biodegradable polymer protective film is one or more of polyvinyl alcohol (PVA), polyethylene glycol (PEG), or starch-based materials; the thermal decomposition initiation temperature of the biodegradable polymer protective film is 180-300℃.

[0055] In one preferred embodiment, the flash point of the biodegradable polymer protective film is below 200°C.

[0056] The function of the coating layer is to ensure the stability of the coated sphere during storage and transportation, and to rapidly degrade at high combustion temperatures, releasing internal functional components in a timely manner to ensure its effectiveness.

[0057] In one preferred embodiment, the thickness of the coating layer is 5-50 μm.

[0058] In one preferred embodiment, the thickness of the reduction catalyst layer is 10-30 μm. If it is too thin, there will be insufficient active components; if it is too thick, it may hinder mass transfer and heat transfer.

[0059] In one preferred embodiment, the thickness of the adsorption layer is 20-60 μm. Sufficient adsorption capacity must be ensured, while excessive thickness should be avoided to prevent the overall particle size of the coated spheres from becoming too large and affecting combustion performance.

[0060] In one preferred embodiment, the thickness of the coating layer is 5-50 μm.

[0061] Based on the same inventive concept, this invention also claims protection for a method for preparing the multilayer core-shell microspheres, comprising the following steps:

[0062] S1. Dry and activate the carrier material;

[0063] S2. Dissolve the catalyst precursor in a solvent, add reducing agent powder to form a uniform suspension; immerse the activated support material from S1 in the suspension and sonicate it; then evaporate the solvent and calcine it.

[0064] S3. Mix the adsorbent and binder at a mass ratio of (5-8):1 to form a slurry, and spray it evenly onto the surface of the material after S2 calcination, and then cure it.

[0065] S4. Dissolve the biodegradable polymer protective film to prepare a coating solution, and coat the material cured in S3 at 60-80℃ to obtain the multilayer core-shell microspheres.

[0066] In one preferred embodiment, in step S1, the carrier material is dried at 100-120°C for 2-4 hours to remove moisture.

[0067] In one preferred embodiment, the activation step S1 is as follows: the dried carrier material is calcined at 300-500°C for 2-4 hours to remove organic impurities, adjust the pore structure and increase surface active groups such as hydroxyl groups, thereby completing the activation.

[0068] Activation aims to increase the number of active sites on the carrier surface.

[0069] In one preferred embodiment, the catalyst precursor is one or more of copper nitrate, ferric nitrate, nickel nitrate, cobalt nitrate, copper chloride, ferric chloride, copper acetate, cobalt acetate, and acetylacetone metal complex.

[0070] In one preferred embodiment, in step S2, the ultrasonic treatment time is 30-60 minutes, the ultrasonic power is 200-500W, and the frequency is 40kHz.

[0071] This parameter helps ensure that the catalyst precursor and reducing agent are uniformly dispersed on the surface and within the pores of the support.

[0072] In one preferred embodiment, in step S2, the solvent is evaporated at 60-80°C.

[0073] In one preferred embodiment, in step S2, the sample is calcined at 300-500°C for 2-4 hours in an inert atmosphere.

[0074] In one preferred embodiment, in step S3, the adhesive is one or more of polyvinyl alcohol, hydroxypropyl methylcellulose, polyacrylic acid, sodium alginate, starch-based adhesive, or silica sol.

[0075] The binder has good film-forming properties, adhesion, and compatibility with the adsorbent material.

[0076] Selection principle:

[0077] Hydroxypropyl methylcellulose (HPMC) / polyacrylic acid (PAA) / sodium alginate: These are water-soluble polymers that are environmentally friendly, non-toxic, and have a moderate decomposition temperature.

[0078] Starch-based binders: low cost and fully biodegradable.

[0079] Silica sol: An inorganic binder that provides excellent thermal stability and mechanical strength.

[0080] In one preferred embodiment, in step S3, the curing temperature is 150-200°C and the time is 30-90 minutes.

[0081] If the curing time is too short (e.g., <30 minutes): the adhesive may not be fully cross-linked and cured at a given temperature, resulting in insufficient mechanical strength of the adsorption layer, which is prone to peeling off during subsequent processing or combustion.

[0082] Excessive curing time (e.g., >90 minutes) can lead to reduced production efficiency, increased energy consumption, and may cause some adsorbent materials (e.g., biochar) to oxidize under prolonged heating, affecting their adsorption performance.

[0083] Based on the same inventive concept, the present invention also claims protection for the application of the multilayer core-shell microspheres in the preparation of fireworks.

[0084] Based on the same inventive concept, this invention also claims protection for a composite fireworks agent, comprising, by weight, 10-30 parts of the multilayer core-shell microspheres, 40-60 parts of oxidant, 10-20 parts of combustible agent, and 3-10 parts of binder.

[0085] In one preferred embodiment, the oxidant is potassium perchlorate.

[0086] In one preferred embodiment, the combustible agent is terephthalic acid or potassium hydrogen terephthalate.

[0087] In one preferred embodiment, the adhesive is a phenolic resin.

[0088] Based on the same inventive concept, this invention also claims protection for a method for preparing the composite fireworks agent, comprising: mixing raw materials evenly and then pressing them under a pressure of 10-20 MPa to obtain the composite fireworks agent.

[0089] Based on the same inventive concept, this invention also claims protection for a composite firework, which is assembled from the composite firework propellant, propellant, effect propellant and fuse.

[0090] Compared with the prior art, the beneficial effects of the present invention are:

[0091] 1. Significant synergistic effect in reducing pollutants:

[0092] Source reduction: The catalyst in the reduction catalyst layer significantly improves the completeness of the combustion reaction and can reduce incomplete combustion products (such as CO and hydrocarbons) by more than 30%.

[0093] End-of-pipe treatment: The adsorption layer treats PM2.5, SO2, and NO generated after the explosion. x It has a highly efficient ability to capture heavy metal particles. Compared with traditional fireworks, the present invention can reduce the concentration of PM2.5 in the environment by about 35-50%. The adsorption layer has a specific fixation effect on heavy metals (such as lead and antimony), effectively preventing them from diffusing into the atmosphere.

[0094] Rapid settling: The coated spheres use larger-diameter porous particles as carriers to transform fine particulate pollutants into larger, heavier aggregates, significantly increasing the settling rate of particulate matter. This reduces the atmospheric suspension time of pollutants by 35-40%, thereby rapidly reducing the exposure risk to people near the ground.

[0095] 2. Enhanced Combustion Performance and Visual Effects: The catalytic effect not only reduces pollution but also increases energy release rate, resulting in more complete and intense combustion. In practice, this manifests as increased brightness and improved color saturation in fireworks, achieving a win-win situation for both environmental protection and visual appeal.

[0096] 3. Resource recycling and cost advantages: The core carrier and adsorption layer can make extensive use of biochar prepared from recycled fireworks waste, realizing the recycling of resources, reducing raw material costs, and conforming to the principles of green chemistry.

[0097] 4. Adaptability to large-scale fireworks displays: This invention fundamentally improves the pollution control capability of a unit of fireworks powder. As described in the literature, the effect of environmentally friendly fireworks can be overwhelmed by the total amount. However, this invention significantly improves the environmental performance of individual products, enabling a 10-15% reduction in the total amount of powder used while achieving the same visual effect, or achieving better performance within strictly limited limits, thus providing a technical path to solve the fundamental problem of "large-scale fireworks displays". Attached Figure Description

[0098] Figure 1 This is a schematic diagram of the structure of the JZCRA sphere;

[0099] Figure 2 This is a flowchart of the JZCRA sphere preparation process;

[0100] Figure 3 This is a schematic diagram of a compound fireworks agent;

[0101] Figure 4 This is a flowchart of the composite fireworks manufacturing process. Detailed Implementation

[0102] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0103] Example 1

[0104] Preparation of JZCRA spheres

[0105] according to Figure 2 The process for preparing JZCRA spheres is as follows:

[0106] Carrier pretreatment: Take biochar derived from waste fireworks (particle size 50-100μm, specific surface area approximately 350 m²) 2 / g, porosity 0.4-0.8cm 3 / g, compressive strength ≥5Mpa, temperature resistance ≥600℃, prepared according to existing technology CN112316967A) 20 g, dried at 110℃ for 3 hours to remove moisture. Then calcined at 300-500℃ in air or inert atmosphere for 2-4 hours to remove organic impurities, adjust pore structure and increase surface active groups such as hydroxyl groups to complete activation.

[0107] Reduced catalyst layer loading:

[0108] Weigh 2.0 g of copper nitrate and 1.0 g of ferric nitrate (catalyst precursor) and dissolve them in 100 mL of deionized water.

[0109] Add 6.0 g of ultrafine aluminum powder (reducing agent, particle size 1-5 μm) and stir to form a suspension. The mass ratio of reducing agent to catalyst is 3:1.

[0110] Add pretreated biochar, sonicate at 40kHz frequency and 300W power for 40 minutes, and evaporate the solvent in an 80℃ water bath.

[0111] The reducing catalytic support was obtained by calcination at 300°C for 4 hours under nitrogen protection. The thickness of the reducing catalytic layer was 10 μm.

[0112] Adsorption layer coating: Modified activated carbon (with a surface area of ​​200-500 m²) is coated. 2 / g, porosity 0.4-0.8cm 3 / g, compressive strength ≥5MPa, heat resistance temperature ≥600℃, Ningxia Huahui Activated Carbon Company, model HX-16 (iodine value ≥900mg / g) 10 g is mixed with 30 mL of 5% polyvinyl alcohol (PVA) solution to form a slurry, and sprayed onto the surface of the carrier from the previous step, and dried at 180℃ for 1 hour. The spray coating steps are as follows: using a fluidized bed coating machine (equipment model Mini-Glatt), coating with 8% PVA solution (inlet temperature 60℃, fluidizing gas velocity 2.5 m / s). 3 / h (atomization pressure of 0.3 MPa), weight gain of 10%. The thickness of the adsorption layer is 10 μm.

[0113] Outer coating: Using a fluidized bed coating machine, 8% PVA aqueous solution was used for coating (inlet temperature 60℃), resulting in a 10% weight gain and forming a dense protective film with a thickness of 10μm, thus obtaining JZCRA spheres. A schematic diagram of the obtained JZCRA spheres is shown below. Figure 1 As shown.

[0114] It is used in the assembly of composite fireworks agents. The formula of the composite fireworks agent is as follows: by weight, 10 parts of coated ball, 60 parts of potassium perchlorate (oxidant), 15 parts of potassium hydrogen terephthalate (combustible agent), 5 parts of phenolic resin (binder), and 10 parts of other additives (composed of 2 parts of copper oxide as color effect agent, 3 parts of calcium stearate as lubricant, and 5 parts of ammonium perchlorate as auxiliary oxidant).

[0115] Information for each reagent is as follows:

[0116] Potassium perchlorate (KClO4, oxidant), manufacturer: Dalian Gaojia Chemical Co., Ltd.; model / specification: industrial grade 1. Purity ≥ 99.0%.

[0117] Potassium hydrogen terephthalate (KC8H5O4, flammable agent), manufacturer: Tianjin Bohai Chemical Group Co., Ltd.; model / specification: chemically pure. Purity ≥99.0%.

[0118] Phenolic resin (binder), manufacturer: Jinan Shengquan Group Co., Ltd., model / specification: thermosetting phenolic resin (Resol type), PF-6601 (solid powder).

[0119] Copper oxide (CuO, colorant), manufacturer: Hengshui Haoyang Chemical Products Co., Ltd., model / specification: industrial grade, purity ≥99.0%, color is black powder.

[0120] Calcium stearate (Ca(C)) 17 H 35 COO )2 (Slip agent / stabilizer), Manufacturer: Hangzhou Oil & Chemical Co., Ltd., Model / Specification: Industrial Grade 1, Calcium content 6.5%±0.5%, Melting point 150-155℃.

[0121] Ammonium perchlorate (NH4ClO4, auxiliary oxidant), manufacturer: Dalian Gaojia Chemical Co., Ltd., model / specification: industrial grade 1, purity ≥99.0%.

[0122] After mixing, the mixture is pressed and molded under 10 MPa pressure for 2 minutes to form composite spheres with a certain mechanical strength and a diameter of 5 mm. A schematic diagram of the resulting composite fireworks agent is shown below. Figure 3 As shown.

[0123] according to Figure 4 The process involves using composite fireworks agents in the assembly of composite fireworks. This composite sphere is then assembled with other fireworks components using traditional techniques to form a complete fireworks product. The specific steps are as follows:

[0124] Filling with effect powder: Take 50 parts by weight of the compound fireworks agent as the effect powder and fill it into the fireworks shell.

[0125] Loading the propellant: Load 5 parts by weight of black powder below the effect powder as the propellant.

[0126] Installation lead wire: Standard fast-burning lead wire is used to ensure reliable connection between the propellant and the effect agent.

[0127] Sealing and molding: Kraft paper and clay are used to seal the cartridge case to ensure uniform sealing pressure and complete the assembly of the fireworks product.

[0128] Applications and Testing:

[0129] Fireworks test: Fireworks were set up in a standard venue, with a PM2.5 monitor (model TSI 8533) placed downwind.

[0130] Data Results:

[0131] PM2.5 peak concentration: 40% lower than traditional fireworks (traditional is 300 μg / m³). 3 In this example, the concentration is 180 μg / m³. 3 ).

[0132] SO2 emission reduction efficiency: The SO2 concentration after combustion was measured using a flue gas analyzer (Model Testo 350). The SO2 concentration for traditional fireworks is calculated at 120 mg / m³. 3 The present invention is 60 mg / m³ 3 The emission reduction efficiency is 50%. Emission reduction efficiency = (SO2 concentration of traditional fireworks - SO2 concentration of this invention) / SO2 concentration of traditional fireworks × 100%.

[0133] Combustion efficiency increased by 15%. Weigh the total mass (m2) of the container and residue after combustion. Calculate the mass of the residue after combustion: m2_residue = m2 - m0. Calculate the mass loss during combustion: Δm = m0_sample - m2_residue.

[0134] Combustion efficiency = (Δm / m0 sample) × 100% Combustion efficiency = (mass before combustion - mass after combustion) / mass before combustion × 100%.

[0135] Example 2

[0136] Alumina-based coated spheres

[0137] The effects of calcination temperature of 250℃ (lower limit) and coated ball content of 30% (upper limit) were verified.

[0138] The preparation process is as follows:

[0139] Carrier pretreatment: γ-Al2O3 (Evonik, Germany, model AEROGEL 300, specific surface area 280 m²) was used. 2 / g, particle size 50-100μm, porosity 0.4-0.8cm 3 / g, compressive strength ≥5Mpa, temperature resistance ≥600℃) 25 g, dried at 110℃ for 3 hours to remove moisture. Then calcined at 500℃ for 4 hours to enhance stability.

[0140] Reduced catalyst layer loading:

[0141] Weigh out 1.5 g of cobalt nitrate and 1.0 g of nickel nitrate, and dissolve them in 80 mL of ethanol.

[0142] Add 10 g of aluminum-magnesium alloy powder (Hunan Jinhao New Materials, model JH-AlMg5 (Mg content 5%)), and the mass ratio of reducing agent to catalyst is 5:1.

[0143] Add pretreated biochar, sonicate at 40kHz frequency and 300W power for 40 minutes, and evaporate the solvent in an 80℃ water bath.

[0144] The reducing catalytic support was obtained by calcination at 300°C for 4 hours under nitrogen protection. The thickness of the reducing catalytic layer was 10 μm.

[0145] Adsorption layer coating: 15 g of molecular sieve MCM-41 was mixed with 50 mL of 3 wt% hydroxypropyl methylcellulose (HPMC) solution to obtain the adsorbent material (with a surface area of ​​200-500 m²). 2 / g, porosity 0.4-0.8cm 3 / g, compressive strength ≥5MPa, heat resistance temperature ≥600℃), spray coating, process is the same as in Example 1. The thickness of the adsorption layer is 10μm.

[0146] Outer coating: Coated with 10% polyethylene glycol (PEG) solution, the weight increased by 12%, forming a dense protective film with a thickness of about 20 μm, thus obtaining JZCRA spheres.

[0147] It is used in the assembly of composite fireworks agents. The formula of the composite fireworks agent is as follows: 30 parts coated ball, 55 parts potassium perchlorate, 12 parts terephthalic acid, 8 parts phenolic resin, and 10 parts other additives (composed of 2 parts copper oxide as a color effect agent, 3 parts calcium stearate as a lubricant, and 5 parts ammonium perchlorate as an auxiliary oxidant).

[0148] After mixing, the mixture is pressed and molded under 10 MPa pressure and held for 2 minutes to form a composite sphere with a certain mechanical strength and a diameter of 5 mm.

[0149] according to Figure 4 The process involves assembling the composite fireworks agents into complete fireworks products, using the same process as in Example 1.

[0150] Data Results:

[0151] PM2.5 peak concentration reduced by 45%: Traditional fireworks have a peak concentration of 300 μg / m³. 3 The result of this example is 165 μg / m³. 3 .

[0152] NOx emissions reduced by 35%: Traditional NO x The concentration was 80 mg / m³, and the result in this example was 52 mg / m³. 3 .

[0153] Combustion temperature increased by 70°C: A thermocouple (such as a type K thermocouple) was inserted into the combustion reaction zone, and the peak temperature was recorded. The reference temperature for conventional fireworks is 1000°C, and the combustion temperature of Example 2 is 1070°C (ΔT = TExample - TConventional).

[0154] Settling time was reduced by 35%. PM2.5 concentration, as recorded by a particulate matter monitor, dropped to background levels (35 μg / m³). 3 The required time is as follows: The settling time of traditional fireworks is 30 minutes, while the settling time of Example 2 is shortened to 19.5 minutes, a reduction rate of 35% (reduction rate = (Ttraditional - Texample) / Ttraditional × 100%).

[0155] Example 3

[0156] Biochar-based coated spheres (preferred center value range)

[0157] The effect of the optimal conditions (20% coated balls, mass ratio 4:1, calcination at 400℃) was verified.

[0158] Based on Example 1, the following parameters are adjusted:

[0159] The reducing catalyst layer was loaded with 2.5 g of copper nitrate, 1.5 g of ferric nitrate, and 10 g of ultrafine aluminum powder (mass ratio 4:1).

[0160] Calcination: 400℃, 3 hours.

[0161] Coated sphere content: 20%. Forms a dense protective film with a thickness of approximately 20 μm.

[0162] Everything else is the same as in Example 1.

[0163] The test results of the composite fireworks showed a 52% reduction in PM2.5 emissions, compared to a PM2.5 concentration of 300 μg / m³ for traditional fireworks. 3 The PM2.5 concentration of the fireworks in Example 3 was calculated to be 144 μg / m³. 3 SO2 concentration below the detection limit (e.g., <1 mg / m³) 3 ).

[0164] Combustion efficiency increased by 22%, and brightness increased by 18%. According to the formula of Example 1 (mass loss method), the combustion efficiency of conventional fireworks is 70%, while the combustion efficiency of the fireworks in Example 3 is increased to 85.4%. Brightness was measured using a photometer (unit: candela). The brightness of conventional fireworks is 1000 cd, while the brightness of the fireworks in Example 3 is 1180 cd.

[0165] Example 4

[0166] Not preferred but within the scope of the claims (10% of the spheres are covered)

[0167] Verify the effect of a 10% coated sphere content (below the preferred range but possibly within the claims).

[0168] Based on Example 1, the following parameters are adjusted:

[0169] The amount of coated spheres was reduced to 10%, forming a dense protective film with a thickness of 20 μm.

[0170] Everything else is the same as in Example 1.

[0171] Tests on the effects of composite fireworks showed a 30% reduction in PM2.5 emissions and an 8% increase in combustion efficiency.

[0172] Example 5

[0173] Not preferred but within the scope of the claims (calcination temperature 350°C)

[0174] The effect of calcination temperature of 350℃ was verified.

[0175] Based on Example 1, the following parameters are adjusted:

[0176] Calcination temperature: 350℃.

[0177] Everything else is the same as in Example 1.

[0178] The effects of the composite fireworks were tested, and the results showed that PM2.5 emissions were reduced by 20%, but the activity of the catalyst was reduced.

[0179] Comparative Example 1

[0180] Based on Example 1, the reduction catalyst layer is omitted.

[0181] The test results of the composite fireworks showed that PM2.5 emissions were reduced by only 13%, and combustion efficiency was not improved.

[0182] Comparative Example 2

[0183] No adsorption layer

[0184] Based on Example 1, the adsorption layer is omitted.

[0185] The test results of the composite fireworks showed that PM2.5 emissions were reduced by 4%, but the ability to capture pollutants was weak.

[0186] Comparative Example 3 (reducing agent only, no catalyst):

[0187] Preparation: Refer to Example 1, but without adding copper nitrate and ferric nitrate (i.e., without catalyst precursor).

[0188] Results: PM2.5 emissions were reduced by approximately 3%, and combustion efficiency was improved by approximately 2%. This demonstrates that in the absence of a catalyst, the reducing agent does not burn completely, resulting in limited emission reduction and efficiency enhancement effects.

[0189] Comparative Example 4 (no reducing agent, only catalyst):

[0190] Preparation: Refer to Example 1, but only add copper nitrate and ferric nitrate, without adding ultrafine aluminum powder.

[0191] Results: PM2.5 emissions were reduced by approximately 2%, and combustion efficiency was improved by approximately 3%. This demonstrates that in the absence of a catalyst, the reducing agent does not burn completely, resulting in limited emission reduction and efficiency enhancement effects.

[0192] Comparative Example 5 (imbalanced ratio of reducing agent to catalyst, 1:1):

[0193] Preparation: Refer to Example 1, but change the amount of aluminum powder to 2.0g, with a mass ratio of 1:1 to the total mass of the catalyst.

[0194] Results: PM2.5 emissions were reduced by approximately 22%, and the combustion reaction was mild but energy release was insufficient. This demonstrates that the low proportion of PM2.5 limited performance.

[0195] Comparative Example 6 (imbalanced ratio of reducing agent to catalyst, 8:1):

[0196] Preparation: Refer to Example 1, but change the amount of aluminum powder to 2.0g, and the mass ratio of aluminum powder to the total catalyst is 8:1.

[0197] Results: PM2.5 emissions were reduced by approximately 16%, and the combustion reaction was mild but energy release was insufficient. This demonstrates that the low proportion limited performance.

[0198] Comparative Example 7 (layer sequence reversed, adsorption layer first, then catalytic layer):

[0199] Preparation: Refer to Example 1, but first coat the core with an adsorption layer, and then load the reduction catalyst layer.

[0200] Results: PM2.5 emissions were reduced by approximately 28%. This demonstrates that incorrect stratification causes the adsorbent material to be sintered and deactivated during the high-temperature combustion stage, while the catalytic layer is encapsulated and cannot function effectively, significantly reducing the synergistic effect.

[0201] Comparative Example 8

[0202] Excessive thickness of the reduction catalyst layer

[0203] Based on Example 1, the thickness of the reduced catalyst layer is 50 μm.

[0204] The test results of the composite fireworks showed that PM2.5 emissions were reduced by 15%, but the ability to capture pollutants was weak.

[0205] Comparative Example 9

[0206] Excessive adsorption layer thickness

[0207] Based on Example 1, the thickness of the adsorption layer is 80 μm.

[0208] The test results for the composite fireworks showed a 28% reduction in PM2.5 emissions and a strong ability to capture pollutants. However, incomplete combustion indicated that an excessively thick adsorption layer would hinder the fireworks' effectiveness.

[0209] Comparative Example 10

[0210] Kernel layer replacement

[0211] Based on Example 1, the core layer was replaced with ordinary activated carbon (manufacturer: Ningxia Huahui Activated Carbon Co., Ltd., model HX-16, specific surface area <300 m² / g).

[0212] The test results of the composite fireworks showed that PM2.5 emissions were reduced by 3%, but the ability to capture pollutants was weak.

[0213] Comparative Example 11

[0214] Omitted covering layer

[0215] Based on Example 1, the coating layer is omitted.

[0216] The effects of the composite fireworks were tested, and the results showed that PM2.5 emissions were reduced by 20%, but the pollutant capture capacity was weak. The reduced PM2.5 emission reduction was due to the premature failure of the adsorption layer caused by the lack of a coating layer, resulting in a 50% decrease in pollutant capture capacity compared to Example 1.

[0217] Comparative Example 12

[0218] The carrier material only has a drying step and lacks an activation step.

[0219] Based on Example 1, the biochar derived from waste fireworks was only dried at 110°C for 3 hours to remove moisture, without subsequent activation.

[0220] The test results of the composite fireworks showed that PM2.5 emissions were reduced by 1.5%, but they could not effectively capture pollutants.

[0221] Comparative Example 13

[0222] Incompatible coating material

[0223] Design: Replace the PVA coating layer in Example 1 with polypropylene (a non-degradable material).

[0224] Result: PM2.5 emission reduction rate dropped to 18% because the coating layer could not degrade in time, the release of the adsorption layer was delayed, and the pollutant capture window was missed.

[0225] Synergistic mechanism disruption: The degradation rate of the coating layer does not match the high temperature of combustion, hindering the temporal synergy of functional layers.

[0226] Comparative Example 14

[0227] Insufficient specific surface area of ​​the carrier

[0228] Design: Replace the kernel layer with a surface area <100m² 2 / g of ordinary ceramic microspheres (biochar from Example 1, specific surface area 350m²) 2 / g).

[0229] Results: PM2.5 emission reduction rate was only 15%, carrier adsorption sites were insufficient, particulate matter aggregation effect was weak, and settling time was not improved.

[0230] Disruption of the synergistic mechanism: The core carrier needs to simultaneously assume the dual roles of "load platform" and "sedimentation promoter", and low specific surface area carriers cannot achieve pollutant fixation.

[0231] Comparative Example 15

[0232] Insufficient thermal stability of the adsorption layer

[0233] Design: The adsorption layer is replaced with ordinary activated carbon (manufacturer: Ningxia Huahui Activated Carbon Company, model HX-16, specific surface area <300 m² / g) (specific surface area <500 m² / g). 2 / g, heat resistance temperature <300℃).

[0234] Results: PM2.5 emission reduction rate was 22%, the adsorption layer structure collapsed in high-temperature flue gas, and the heavy metal capture capacity was lost.

[0235] Synergistic mechanism failure: The adsorption layer needs to maintain structural stability in the high-temperature environment after combustion. Insufficient thermal stability directly leads to the failure of end-of-pipe treatment.

[0236] Comparative Example 16

[0237] Traditional fireworks

[0238] Formula: Black powder base (potassium nitrate, charcoal, sulfur).

[0239] The basic formula of typical black powder is based on the Chinese national standard "Safety and Quality of Fireworks and Firecrackers" to reflect the closest existing technology.

[0240] Specific formula (parts by weight):

[0241] Potassium nitrate (KNO3, oxidizing agent): 75 parts

[0242] Charcoal (C, combustible): 15 parts

[0243] Sulfur (S, flammable agent and adhesive): 10 parts

[0244] (Note: This ratio is one of the standard proportions for black powder, denoted as KNO3:C:S = 75:15:10)

[0245] Preparation process:

[0246] Raw material pretreatment: Potassium nitrate, charcoal, and sulfur are crushed separately and passed through an 80-mesh sieve.

[0247] Mechanical mixing: Place the three sieved raw materials in a ball mill according to the above proportions and mix for 2 hours to ensure uniformity.

[0248] Compression molding: The uniformly mixed black powder is compressed under a pressure of 5MPa and held under pressure for 1 minute to obtain a traditional firework powder column.

[0249] Test results:

[0250] PM2.5 peak concentration: ~300 µg / m³ 3 .

[0251] Particulate matter settling time: >30 minutes (referring to the time required for the PM2.5 concentration at the site to return to the background value after the fireworks display).

[0252] Combustion efficiency: low, with noticeable smoke and sulfur odor.

[0253] To verify its adaptability to the total amount of fireworks used, a comparative test of equal amounts of explosives was conducted. 15 kg of the composite fireworks explosives from Example 1 and 17 kg of the traditional environmentally friendly fireworks explosives from Comparative Example 11 were used for fireworks displays. The results showed that the total PM2.5 generated by Example 1 was still 25% lower than that of the traditional method, demonstrating its advantage in pollution control per unit of explosives. This allows for a reduction in the total amount of explosives used while achieving the same visual effect, thus technically addressing the issue of large-scale fireworks displays.

[0254] The four-layer structure of the multilayer core-shell microspheres of this invention achieves synergistic effects through functional complementarity and spatiotemporal coupling: the core layer (such as biochar, γ-Al2O3) has a high specific surface area (≥200m²). 2 / g) and porosity (0.4–0.8 cm⁻¹) 3 / g) provides dispersion anchoring points for the reduction catalyst layer. Ultrasonic loading and calcination (300–500℃) ensure that the catalyst (e.g., CuO / Fe2O3) and the reducing agent (e.g., aluminum powder) form uniform active micro-regions, improving combustion efficiency and reducing pollutant generation from the source. The reduction catalyst layer acts preferentially during the combustion stage, reducing the treatment load on the subsequent adsorption layer, while the high combustion temperature activates the adsorption layer's activity. The adsorption layer (e.g., modified activated carbon) instantly captures gaseous pollutants (SO2, NO) after combustion. x The catalytic layer removes heavy metals and promotes particulate matter agglomeration and sedimentation through a core carrier. The coating layer (such as a PVA film) keeps the particles dry and active during storage and degrades rapidly during combustion to precisely release the adsorption function. In Examples 1-3, the PM2.5 emission reduction rate reached 40%–52% when the four-layer structure was intact, while Comparative Example 7 (layer sequence reversed) only achieved 28% and Comparative Example 10 (carrier not activated) only achieved 20%. This demonstrates that the layer sequence, parameter matching (such as catalytic layer thickness of 10–30 μm and adsorption layer heat resistance ≥600℃) and time sequence linkage (closed loop of catalysis-adsorption-sedimentation) are key to the synergistic effect. Failure of any link will lead to a significant decrease in pollution control capability.

[0255] It should be noted that the above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A multilayer core-shell microsphere, characterized in that, It comprises a four-layer structure consisting of a core layer, a reduction catalytic layer, an adsorption layer, and a coating layer; the core layer is coated with a reduction catalytic layer, the reduction catalytic layer is coated with an adsorption layer, and the adsorption layer is coated with a coating layer. The core layer is composed of a carrier material with a specific surface area of ​​200-500 m². 2 / g, porosity 0.4-0.8cm 3 / g; The reduction catalytic layer includes a reducing agent and a catalyst; The adsorption layer includes an adsorption material; The coating layer is a biodegradable polymer protective film.

2. The multilayer core-shell microspheres according to claim 1, characterized in that, The carrier material is one or more of activated alumina, biochar, silica gel, porous ceramic microspheres, mesoporous silica, or molecular sieve; the compressive strength of the carrier material is ≥5MPa, and the heat resistance temperature is ≥600℃.

3. The multilayer core-shell microspheres according to claim 1, characterized in that, In the reduction catalyst layer, the mass ratio of reducing agent to catalyst is (3-5):1; the reducing agent is one or more of aluminum powder, magnesium powder, boron powder, silicon powder, titanium powder, zirconium powder, or aluminum-magnesium alloy powder, with a particle size of 1-10 μm; the catalyst is CuO, Fe2O3, Co3O4, or MnO. 2、 One or more of Cr2O3, NiO, V2O5, Pt, Pd or their oxides.

4. The multilayer core-shell microspheres according to claim 1, characterized in that, The adsorbent material is a porous material with a surface area of ​​200-500 m². 2 / g, porosity 0.4-0.8cm 3 / g, compressive strength ≥5MPa, heat resistance temperature ≥600℃; the adsorbent material is one or more of modified biochar, activated carbon or metal-organic framework materials, zeolite, diatomaceous earth, hydrotalcite, and graphene oxide.

5. The multilayer core-shell microspheres according to claim 1, characterized in that, The biodegradable polymer protective film is one or more of polyvinyl alcohol (PVA), polyethylene glycol (PEG), or starch-based materials.

6. The multilayer core-shell microspheres according to any one of claims 1-5, characterized in that, The thickness of the coating layer is 5-50 μm; the thickness of the reduction catalyst layer is 10-30 μm; and the thickness of the adsorption layer is 20-60 μm.

7. The method for preparing multilayer core-shell microspheres according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Dry and activate the carrier material; S2. Dissolve the catalyst precursor in a solvent, add reducing agent powder to form a uniform suspension; immerse the activated support material from S1 in the suspension and sonicate it; then evaporate the solvent and calcine it. S3. Mix the adsorbent and binder at a mass ratio of (5-8):1 to form a slurry, and spray it evenly onto the surface of the material after S2 calcination, and then cure it. S4. Dissolve the biodegradable polymer protective film to prepare a coating solution, and coat the material cured in S3 at 60-80℃ to obtain the multilayer core-shell microspheres.

8. The preparation method according to claim 7, characterized in that, In step S1, the activation step is as follows: the dried support material is calcined at 300-500℃ for 2-4 hours; the catalyst precursor is one or more of copper nitrate, ferric nitrate, nickel nitrate, cobalt nitrate, copper chloride, ferric chloride, copper acetate, cobalt acetate, and acetylacetone metal complex.

9. A composite fireworks agent, characterized in that, By weight, it comprises 10-30 parts of the multilayer core-shell microspheres as described in any one of claims 1-6, 40-60 parts of oxidant, 10-20 parts of combustible agent, and 3-10 parts of binder.

10. A composite firework, characterized in that, It is assembled from the composite fireworks agent as described in claim 9, the propellant, the effect agent, and the fuse.

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